1. Field of the Invention
The present invention relates to hand tools, such as pliers, and relates in particular to slip-joint pliers incorporating a bias mechanism to resiliently bias the pliers to an open condition.
2. Description of the Prior Art
In slip-joint pliers the two levers of the pliers are joined by a pivot shaft, such as a bolt, extending through holes in the pivot portions of the two levers, one of the holes substantially matching the cross-sectional size and shape of the shaft, and the other hole being elongated so as to accommodate a lateral shifting of the associated lever among different positions relative to the shaft.
Heretofore, it has been known to provide a bias mechanism for resiliently biasing pliers levers to an open condition for working convenience, such bias mechanism commonly being in the form of a torsion spring partially or completely encircling the pivot shaft. The use of such a bias mechanism in slip-joint pliers is disclosed, for example, in U.S. Pat. Nos. 1,657,348 to Drum and 4,669,340 to Igarashi, the former disposing the bias spring between the levers in recesses formed in the facing surfaces of the levers. However, in each of these devices, the ends of the spring are, respectively, turned outwardly in directions substantially perpendicular to the plane of the spring coil and are accommodated in bores or grooves in the recesses. This requires not only the formation of a spring with appropriately bent ends, but also requires the formation of multi-level recesses with additional bores or grooves formed therein, adding to the expense of manufacture.
A biasing torsion spring in a non-slip-joint crossed-lever tool is disclosed in U.S. Pat. No. 2,392,118 to Cacarillo. In this device the spring ends are tangent to the coil and are not inclined to the plane of the coil, but the spring recesses have central bosses formed therein to separate the spring from the pivot shaft, and also have narrow arms extending outwardly from the main body of the recess substantially tangent thereto for respectively receiving the spring ends. Again, this complex recess construction adds to the expense of manufacture of the tool.